In the following text, if not otherwise stated, the following meanings are used:
CSI chlorosulfonyl isocyanate
CSOS chlorosulfonic acid
ClSI bis(chlorosulfonyl)-imide
FSI fluorosulfonyl isocyanate
FSOS fluorosulfonic acid
FR flow rate
RT room temperature
Imidodisulfuryl compounds are used for a number of purposes. One example is the use of imidodisulfurylchlorid for the preparation of lithium bis(fluorosulfonyl)imid, which again is used as an electrolyte e.g. in lithium ionic batteries, which e,& can be used in automotive batteries, and is used as antistatic agent in touch screens.
DE 1 159 410 B discloses a method for preparation of halosulfonyl isocyanates by a reaction of halosulfonic acid with urea. The reaction is done preferably at a temperature of from 100 to 180° C. Specifically disclosed is the preparation of chlorosulfunyl isocyanate at a temperature of from 120 to 150° C.
DE 1 143 495 B discloses a method for preparation of imido-bis(sulfuryl)fluorid by a reaction of fluorosulfonic acid with urea. The reaction temperature is not stated apparently the reaction starts at room temperature and in the course of the reaction the reaction mixture is cooled from time to time.
CA 710255 A discloses a method for preparation of imido-bis(sulfurylchloride) by a reaction of chlorosulfonic acid with trichlorophosphazo-sulfuryl chloride. Methods such as disclosed in CA 710255 have the disadvantage of requiring phosphorus chemistry which is rather expensive and environmentally disadvantageous to use.
WO 20091123328 A1 discloses the preparation of ClSI in a batch method, details are given the example section of instant invention.
The reaction equation of instant invention for preparation of imidodisulfurylhalides, also named imidobis(sulfurylhalides), imidobissulfurylhalides or bis(halidosunnyl)imide, which also is applicable for similar compounds of instant invention, is depicted in Scheme 1;
with Xa and Xb being halogen.
Both starting compounds, the isocyanate and the sulfonic acid, and the product, the his imide, are toxic and corrosive. In case of Xa and Xb being Cl, the product shows a very high exothermic decomposition at elevated temperatures, making it necessary to provide adequate safety measures in production. The heat of reaction deltaH is ca. 100 kJ/mol, the onset of decomposition of the imidosulfurylchloride is around 180° C. with an adiabatic temperature rise to temperatures well over 400° C. The reaction of CSI with FSOS and the reaction of PSI with CSOS show similar temperatures for the onset of decomposition.
Therefore the reaction temperature in batch processes in production is not higher than 150° C. to avoid the risk of explosion. The reaction times of the batch processes ranges from ca, 8 h to 24 h.
On the other hand the isocyanate and the sulfonic acid only react at elevated temperatures. Due to these circumstance and safety considerations, in the past the imidodisulfurylhalides have been prepared only in small batches and at temperatures well below the onset of decomposition as mentioned, leading to the mentioned long reaction times.
There was a need for a method for preparation of imidodisulfurylhalides, which does not need phosphorous chemistry, has short reaction times and high yields, where the product shows high purity, and allows for safe handling of the substances and of the reaction, also on a large scale.
Unexpectedly, it is possible to react a halosulfonyl isocyanate with a halosulfonic acid at temperatures above the onset temperature of decomposition of the reaction product, the imidodisulfurylhalide without the expected decomposition of the desired imidodisulfurylhalide, the yields are high. It was unexpected to be able to conduct the reaction in a safe way. This allows for the desired short reaction times.
Furthermore the short reaction times can be realized still with a product with high purity, i.e. not showing discoloration due to decomposition or polymerization reactions usually taking place at too high temperatures.